Trapezium implant for thumb and method

ABSTRACT

An implant for the trapezium of the thumb carpometacarpal (CMC) joint comprising an integral elastomeric member configured to include a body portion having a tapered neck, having extending from one end thereof an elongated, longitudinally extending tapered portion adapted to be embedded into a reamed out-channel in the thumb metacarpal bone. After implantation, in the preferred embodiment of the method according to the invention, a segment of a nearby tendon, for example, the APL or FCR tendons, may be wrapped around the tapered neck of the implant to secure it in position, thereby forming a reinforced structure to inhibit dislocation of the prosthesis. However, in other methods, various other securing elements, including, but not limited to acellular matrices, may be used to retain the implant in position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 10/842,030, filed on May 7, 2004, the entirety of which isherein incorporated by reference.

BACKGROUND OF THE INVENTION

Freedom from pain is essential for normal thumb function. Although thecarpometacarpal (CMC) joint of the thumb is described as a saddle joint,it is actually formed by apposed saddles, one astride the other, eachone's longitudinal axis perpendicular to the other. Such a relationshipcreates a joint where two primary planes of motion, flexion-extensionand adduction-abduction, are perpendicular to one another. With rotarymovement such as opposition and circumduction, the surfaces are twistedinto a less congruous relationship, causing tightening of the jointcapsule and thereby increasing joint stability, provided all ligamentsare competent.

Idiopathic hypermobility of the thumb basal joint is not uncommon,particularly in women, and would seem to be a major factor in producingthe arthrosis which so frequently afflicts the CMC joint. Trauma, acuteor recurrent, causing partial tears or stretching of the ligaments,likewise will produce varying degrees of hypermobility. Undetectedarticular damage may also accompany such trauma, thereby compounding thepathological process. When painful hypermobility is present, restorationof ligament stability will not only relieve the pain and stabilize thejoint, but, when done prior to the onset of articular damage, mayprevent or at least retard subsequent joint degeneration. A ligamentreconstruction procedure for painful, unstable thumb carpometacarpal(CMC) joint is presented in an article entitled “Ligament Reconstructionfor the Painful Carpometacarpal (CMC) Joint,” by Eaton, and Littler,which appears in the Journal of Bone and Joint Surgery, Vol. 55-A, No.8, pp. 1655-1666, December, 1973.

For more advanced arthrosis, ligament reconstruction is not sufficient.Advanced arthrosis is generally recognized by the obvious dorsalsubluxation of the metacarpal base. As the base of the thumb metacarpalsubluxates dorsally, there is a reciprocal flexion-abduction of themetacarpal shaft, and frequently flexion-adduction contracture of theentire thumb ray. Carried to the extreme deformity, themetacarpophalangeal joint compensates for the metacarpalflexion-adduction position by hyperextending and the joint may becomefixed in this hyperextended position. These sequential compensationdeformities must be recognized and corrected at the same time asreconstruction of the basal joint is carried out.

Heretofore, deformities of the carpometacarpal (CMC) joint have beenundertaken utilizing a trapezium prosthesis, and implanting theprosthesis following removal of the diseased trapezium bone. One knownprosthesis comprises an integral elastomeric member, preferably of aflexible silicone material, having a cylindrical base portion from oneend of which extends a triangular cross-sectioned tapered projectionadapted to be imbedded into the reamed-out channel in the thumbmetacarpal bone. In view of the very slippery, low coefficient surfaceof the material of the prosthesis, and the fact that the elastomericmaterial of the prosthesis is difficult to handle and will not hold astitch, when implanted, the prior art prosthesis has a tendency to slipout of place in that the opposite end of the cylindrical portion of theprosthesis merely rests against the adjacent navicular. Furthermore,when implanted, the amount of force applied by the patient, in apinching direction of the hand, must be limited in order to preventinadvertent popping out of the prior art prosthesis. Still further, inorder to insure as close a fit as possible, in order to minimizeslipping out of position of the prosthesis, several different sizes ofprosthesis must be manufactured, and by trial and error implanted intothe patient's hand.

Another form of known prosthesis or trapezium prosthesis is of thegeneral shape of the prior art device described above with the additionof several elastomeric tails or extending elements which are loopedaround a structure of the palmer aspect of the hand in an attempt tokeep the prosthesis from dislocating dorsally.

As is readily apparent, considering the type of material which must beemployed for an implantable prosthesis, the tails or extending elementsare extremely fragile, and tend to wear and break thereby losing thefixation sought to be obtained. In addition, it is difficult to firmlysecure the elastomeric tails to the hand structure, thereby resulting inthe patient having to limit the use of his hand with reference to theapplication of hand grip forces.

Accordingly, there is room for improvement within the art.

OBJECTS OF THE INVENTION

It is an object of the invention to provide a trapezium implant ofincreased strength and longevity.

It is an object of the invention to provide a trapezium implant that isless likely to become dislodged from its proper positioning.

It is an object of the invention to provide a trapezium implant that iseasy to implant and firmly position.

These and other objects of the invention are achieved by an implant forthe trapezium of the thumb carpometacarpal joint comprising an integral,elastomeric member including a body portion having: an elongated,longitudinally extending tapered portion extending from one end of thebody portion; and a tapered neck.

These and other objects of the invention are achieved by a method ofreconstructing the carpometacarpal (CMC) joint of a thumb, including thesteps of: a) implanting an implant having an elongated tapered portionand a tapered neck into the joint; b) stripping away a portion oftendon, leaving the distal attachment intact adjacent the implant; c)wrapping the split tendon around the tapered neck of the implant to apoint intersecting the remaining tendon at the palm side of the hand,and suturing the split tendon to the remaining tendon.

These and other objects of the invention are achieved by a method ofreconstructing the carpometacarpal (CMC) joint of a thumb, including thesteps of: a) implanting an implant having an elongated tapered portionand a tapered neck into the joint; b) providing a securing element; c)attaching the securing element to a tendon; d) wrapping the securingelement around the tapered neck of the implant to a point intersectingthe tendon at the palm side of the hand, and attaching the securingelement to the tendon.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary embodiment of a trapeziumprosthesis according to the subject invention;

FIG. 2 is a side view of of an exemplary embodiment of a trapeziumprosthesis according to the subject invention;

FIG. 3 is a top view of a thumb and the surgically implanted exemplaryembodiment of the trapezium prosthesis according to the subjectinvention; and

FIG. 4 schematically illustrates the completed surgically implantedexemplary embodiment of the trapezium prosthesis as firmly fixed inplace in an exemplary method by the use of a portion of the patient'snatural tendon.

FIG. 5 schematically illustrates the completed surgically implantedsecond exemplary embodiment of the trapezium prosthesis as firmly fixedin place in an exemplary method by the use of a tendon substitute.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the figures, an exemplary embodiment of a trapeziumprosthesis/implant for the thumb that meets and achieves all theabove-mentioned objects of the invention will now be described.

Referring to FIGS. 1 and 2, the exemplary embodiment of the trapeziumimplant according to the invention is generally designated by thenumeral 10 and comprises an integral elastomeric member, preferably asilastic material such as silicone rubber, and which is inherentlyflexible and physiologically inert. The implant 10 includes a bodyportion 12 having tapered conical portions 15 and 17 separated by atapered neck 20. Tapered portions 15 and 17 have end faces 14 and 16,respectively. Integrally formed and projecting from the end face 14 isan elongated, longitudinally extended tapered portion 18 which extendsalong the longitudinal axis L of implant 10. Tapered portion 18 willhave a length d₂ that is typically equal to 3 (three) times the lengthd₁ of body portion 12 so as to assure the overall integrity of thereconstructed joint. Tapered portion 18 should preferably have asubstantially constantly decreasing taper (at least in the area of end19), unlike the more variable taper shown in the implant depicted inU.S. Pat. No. 3,924,276, whose contents are incorporated by referenceherein in their entirety. The end 19 of the tapered portion 18 isblunted, preferably with a generally hemispherical tip only at its end,unlike the more pointed configuration shown in the '276 patent. Thetapered portion 18 has a preferably generally annular (i.e., circular)cross-section to reduce residual stresses in implant 10. However,polygonal cross-sections, such as triangular cross-sections describedabove, may be used. Additionally, the proximal end of tapered portion 18should merge into end face 14 of tapered portion 15 via a sweepingcurve, typically having a radius r of approximately 3/32 inches. Asweeping curve, rather than a sharp projection such as shown in the '276patent or other prior art trapezium implants, assures the structuralintegrity of the overall implant.

The opposite end face 16 of body portion 12 has a slightly concavedepression 11 in order to more effectively cooperate with the navicularor scaphoid bone 40 (see FIGS. 3 and 4), as will be more particularlydescribed hereinafter.

As previously mentioned, extending transverse to the longitudinal axis Lof the implant 10, and more particularly radially through the bodyportion 12 is a tapered neck 20. Tapered neck 20 will preferably have acircular cross-section. The diameter of the tapered neck 20 is suitablydimensioned relative to the size of the body portion 12 and the materialfrom which it is made to prevent breaking of the implant 10, and yetsmall enough to fully accommodate the portion of the tendon which is tobe wrapped there around, as will be described below. Rims 13 of taperedportions 15, 17 should preferably be rounded, rather than squared toreduce residual stresses in implant 10 and increase its overall strengthand longevity.

FIGS. 3 and 4 illustrate steps in the method of applicant's invention.As shown in FIG. 3, in the subject process of reconstructing the thumbcarpometacarpal (CMC) joint 34 following the surgical removal of thediseased trapezium, the surgeon then performs the step of hollowing outthe lining of the marrow cavity of the metacarpal bone 36 utilizingconventional techniques and conventional apparatus such as an electricreaming device in order to define any elongated cavity 38 in themetacarpal bone 36. The implant 10, and more particularly the elongatedextended portion 18, is inserted into the cavity 38. The base or endface 16 of the implant 10 should fit in good contact circumferentiallywith the cortex or outer portion of the thumb metacarpal 36 so that ithas even pressure around the entire contact surface. Likewise theopposite end face 16, with its slightly concave depression 11, shouldfit in good firm contact with the navicular or scaphoid 40. In somecases, it may also be desirable to sculpt the lower 5 mm of thetrapezoid (not shown) to permit the lower portion of the implant 10 tosit atop the scaphoid 40 while not interfering with the scaphotrapezoidjoint (not shown). Reference should be made to U.S. Pat. No. 5,913,818,commonly assigned with this patent application and incorporated byreference herein, for a depiction of the relationship of the trapezoidto the scaphoid.

The next step in the preferred method is to obtain a strip of adjacenttendon, for which is suggested the use of the abductor pollicis longus(APL) tendon or the flexor carpi radialis (FCR) tendon. Throughconventional technique, two incisions are made above the wrist, and themain tendon body 50 is partially cut across its width as at 52, andstripped along the longitudinal line 54 to obtain a strip 56 of about 6centimeters in length. However, the doctor has great flexibility in thisregard. This segment 56 is tunneled under the skin to emerge at thewrist in the vicinity of the metacarpal joint, after which the free endof the tendon strip 56 is directed around the tapered neck 20 of theimplant 10 (see FIG. 4) and then penetrated through the residual capsuleattached to the metacarpal 36 at a point which is perpendicular to theplane of the thumb nail 32, and then the tendon strip 56 is passed tothe remaining main tendon body, as at point 58, at the palm side of thenew reconstructed joint. The strip 56 is fixed, such as by means of twostitches, to the main tendon body 50 on the dorsal side of the hand, atthe point where it wraps around the tapered neck 20 the implant 10 onthe dorsal of the wrist, and then likewise the implant 10 is pulled intoplace by pulling on the ligament, thereby seating it into its socket,and then a second suture is placed between this new ligament and themain tendon body 50. The free tail 60 usually represents about 4centimeters, and this free tail is then interwoven across and around theimplant 10 to form a new capsule for the metacarpal joint. The use of atendon as a building material to weave a new capsule provides anextremely strong and durable construction, since it is thicker than thenatural capsule, and of course, since it is the patient's own tissue itcannot and will not be rejected. It will adhere to any normal tissue,and it will not adhere to the elastomeric material of the implant 10. Ofcourse, the tendon does not have to adhere to the implant 10 since itpasses around the tapered neck 20 of the implant 10 and therefore firmlysecured to the implant 10.

In some patients, where there is sufficient quality capsular tissue,suture (not shown) may be passed around the tapered neck 20 and sewn tothe capsule to provide implant 10 stabilization; tendon will not have tobe used.

While the preferred method according to the invention is to use, forexample, a portion of the patient's APL or FCR tendon to keep implant 10in position, the method is not so limited. First, connective tissue maybe harvested from any other suitable location on the patient as is wellknown in the art. Second, and less preferable, allograft may be usedafter the proper tissue matching and pathogen purification protocols arefollowed. Third, organically derived acellular matrices, which do notpose tissue matching due to their processing, may be used. Examples ofsuch matrices, used in other applications can be found in, for example,U.S. Pub. 2002/072806; U.S. Pat. No. 6,206,931. However, a preferredacellular matrix would comprise Graftjacket® acellular matrix, sold byWright Medical Technology, Inc., of Arlington, Tenn., and manufacturedaccording to U.S. Pat. Nos. 4,865,871; 5,024,830; and 5,336,616. Thisproduct consists of a selectively preserved extracellular protein matrixthat is devoid of certain viable cells which normally express majorhistocompatibility complex antigenic determinants and other antigenswhich would be recognized as foreign by the recipient. Thisextracellular protein matrix is made up of collagen and other proteinsand provides a structural template which may be repopulated with newviable cells that would not be rejected by the host. With this materialcomplications following implantation (including but not limited toimmunorejection, contracture, calcification, occlusion, and infection)are significantly reduced relative to current implant procedures andmaterials. Finally, synthetic porous materials capable of connectivetissue in-growth may be used. See e.g. U.S. Pat. No. 5,258,040.

Any of these exemplary materials, comprising a tendon substitute, may befixed to the existing tendon using any known method and then wrappedaround implant 10 as described above. This is shown in FIG. 5. Forexample, material M is sutured to the distal portion 50′ of tendon 50using suture S. Then, material M is manipulated as tendon strip 56described above was to secure implant M in position.

Therefore, using either the patient's natural tendon or a tendonsubstitute as a securing element in combination with implant 10, theresulting reconstructed metacarpal joint is significantly stronger, moredurable, and easier to implant than prior art reconstructed joints usingconventional prosthesis. For example, in U.S. Pat. No. 3,924,276,several shortcomings are inherent in the design. First, the radialaperture causes the overall implant to be weaker. Second, there is theadditional step of properly aligning the aperture. Third, there is theoverall difficulty in threading the tendon through the aperture. None ofsuch steps or difficulties are present in the inventive design while allthe benefits of the '276 patent are achieved if not exceeded, e.g., gripstrength.

To those skilled in the art to which this invention relates, manychanges in construction and widely different embodiments andapplications of the subject process and device will suggest themselveswithout departing from the spirit and scope of the invention. Thedisclosures and descriptions herein are purely illustrative and are notintended to be in any sense limiting.

That which is claimed:
 1. A method of reconstructing a carpometacarpal(CMC) joint of a thumb of a hand, comprising: a) implanting an implanthaving an elongated tapered portion and a tapered neck into the CMCjoint; b) stripping away a portion of a tendon to leave a distalattachment intact adjacent to the implant; c) wrapping the tendon aroundthe tapered neck of the implant to a point intersecting a remainingtendon at a palm side of the hand; and d) suturing the tendon to theremaining tendon.
 2. The method of claim 1, wherein step b) includesstripping away a portion of a flexor carpi radialis (FCR) tendon.
 3. Themethod of claim 1, wherein step b) includes stripping away a portion ofan abductor pollicis longus (APL) tendon.
 4. The method of claim 1,wherein the elongated tapered portion is inserted into a cavity formedin a metacarpal until an end face of an internal bulge of the implantcircumferentially contacts a cortex of the metacarpal.
 5. The method ofclaim 4, wherein the tapered neck is disposed between the internal bulgeand an articulation bulge of the implant.
 6. The method of claim 5,wherein the tapered neck has a cross-sectional area that is less than across-sectional area of the internal bulge and a cross-sectional area ofthe articulation bulge.
 7. A method of reconstructing a carpometacarpal(CMC) joint of a thumb of a hand, comprising: a) implanting an implanthaving an elongated tapered portion and a tapered neck into the CMCjoint; b) attaching a securing element to a tendon at a first location;c) wrapping the securing element around the tapered neck of the implantto a point intersecting the tendon at a palm side of the hand; and d)attaching the securing element to the tendon at a second location. 8.The method of claim 7, wherein the securing element includes a tendonsubstitute.
 9. The method of claim 8, wherein the tendon substituteincludes an acellular matrix.
 10. The method of claim 7, wherein theelongated tapered portion is inserted into a cavity formed in ametacarpal until an end face of an internal bulge of the implantcircumferentially contacts a cortex of the metacarpal.
 11. The method ofclaim 10, wherein the tapered neck is disposed between the internalbulge and an articulation bulge of the implant.
 12. The method of claim11, wherein the tapered neck has a cross-sectional area that is lessthan a cross-sectional area of the internal bulge and a cross-sectionalarea of the articulation bulge.
 13. A method of reconstructing acarpometacarpal (CMC) joint of a thumb of a hand, comprising: a)inserting an elongate tapered portion of an implant into a cavity formedin a metacarpal until an end face of an internal bulge of the implantcircumferentially contacts a cortex of the metacarpal; b) positioning ascaphoid such that the scaphoid is in contact with a proximal face of anarticulation bulge of the implant; c) stripping away a portion of atendon to leave a distal attachment intact adjacent to the implant; d)wrapping the tendon around a tapered neck of the implant to a pointintersecting a remaining tendon at a palm side of the hand, the taperedneck disposed between the internal bulge and the articulation bulge ofthe implant such that the tapered neck encircles the implant in adirection that is substantially perpendicular to a longitudinal axis ofthe elongate portion of the implant; and e) suturing the tendon to theremaining tendon.
 14. The method of claim 13, wherein the tapered neckhas a cross-sectional area that is less than a cross-sectional area ofthe internal bulge and a cross-sectional area of the articulation bulge.15. The method of claim 13, wherein the elongate tapered portionincludes an annular cross section and a substantially constant taper.16. The method of claim 13, wherein the tapered neck includes a concavearcuate juncture formed between a proximal surface of the internal bulgeand a distal surface of the articulation bulge.
 17. The method of claim16, wherein the concave arcuate juncture is symmetric about alongitudinal axis of said implant.
 18. The method of claim 16, whereinthe concave arcuate juncture flattens out to include a low-archedcentral region.
 19. The method of claim 13, wherein step c) includesstripping away a portion of a flexor carpi radialis (FCR) tendon. 20.The method of claim 13, wherein step c) includes stripping away aportion of an abductor pollicis longus (APL) tendon.